Electrical switch with floating bridge contact structure



Aug. 16,

Filed Oct.

Ill m 1' M ill I P. E. VEGA ELECTRICAL SWITCH WITH FLOATING BRIDGECONTACT STRUCTURE 2 Sheets-Sheet 1 a I o O 0 Z 25 o O 0 9 OO HTTORNEY5INVENTOR. P601. E. VEGH Aug. 16, 1966 P. E. VEGA 3,267,224

ELECTRICAL SWITCH WITH FLOATING BRIDGE CONTACT STRUCTURE Filed Oct. 17,1962 2 Sheets-Sheet 2 INVENTOR PfiUl. E. V581? flT TORNE Y6 UnitedStates Patent 3,267,224 ELECTRICAL SWITCH WITH FLOATING BRIDGE CONTACTSTRUCTURE Paul E. Vega, North Hollywood, Calif., assignor to AerovoxCorporation, New Bedford, Mass., a corporation of Massachusetts FiledOct. 17, 1962, Ser. No. 231,135

2 Claims. (Cl. 20011) This invention relates to the art of electricalswitches, more particularly to an improved instrument switch permittingselective completion of any one or more of a plurality of desiredcircuits by manipulation of the switch.

As conducive to an understanding of the invention, it is noted that avariety of so-called instrument switches have been evolved in which anelectrical circuit is completed between a commutator ring and one ormore of a plurality of spaced contacts whereby the circuits coupled tosaid spaced contacts may be selectively energized or de-energized bymoving -a brush member over the commutator into electrical connectionwith the desired contacts. In order to obtain an effective and efficientswitching function permitting utilization with delicate instruments, itis desirable to insure positive metal to metal contact between thebrushes and the commutator ring and contacts thereby preventing a highresistance connection. It is further desirable to reduce frictionbetween moving components so as to minimize wear and increase theservice life of the switch.

It is accordingly among the objects of this invention to provide anelectrical switch permitting eificient selective making or breaking ofone or more of a plurality of electrical circuits with positive metal tometal contact and with a minimum number of elements that are not likelyto become deranged even with long use.

According to one illustrative embodiment of the invention, theinstrument switch comprises a contact plate of insulating material uponwhich one or more commutator rings are supported along with a pluralityof spaced contacts. Terminal connectors extend through the contact platefrom each of the contacts, and from the commutator ring, to facilitatetheir electrical connection in a circuit to be controlled by the switch.A brush block assembly including a brush supporting plate of insulatingmaterial is rotatably mounted with respect to said contact plate. Aplurality of pairs of openings are formed in the brush supporting plateand a U-shaped brush member is arranged loosely on the supporting platewith the legs of the brush member extending through said openings. Oneleg of the brush member extends into wiping cont-act with a commutatormember and the other leg extends into wiping contact with a contact. Acantilever spring having one end anchored to the brush supporting platehas a foot at its free end, biased against the brush member to force thelegs through the openings against the contact and commutator. The footcontacts the brush member with substantial point contact providing afulcrum on which the brush member may rock. A mounting plate is arrangedat a spaced distance from the contact plate, and a shaft extendsrotatably through said mounting plate into engagement with said brushsupporting plate so that by manipulation of a knob on the free end ofthe shaft the brushes may bemoved to a desired contact. A star wheel isdesirably secured to the shaft for rotation therewith and a springpressed rollerdetent engages between the teeth of the star wheeltoprovide stepping movement of the brush block assembly with respect tothe contact plate.

In the accompanying drawings in which are shown one or more of variouspossible embodiments of the several features of the invention;

' of like radius of curvature.

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FIG. 1 is a side elevational view of the novel instrument switch,

FIG. 2 is a bottom plan view of the switch showing the terminals of thecommutator rings and contacts,

FIG. 3 is an enlarged cross-sectional view on line 3-3 of FIG. 2illustrating the desired relationship between switch components,

FIG. 4 is a cross sectional view on line 44 of FIG. 3 illustrating thetop of the brush block assembly, and,

FIG. 5 is an enlarged detailed view of the star wheel and spring pressedroller detent controlling the stepping action of the brushes betweencontacts.

As shown in the drawings, the instrument switch 10 comprises a contactplate 11, here shown of a square configuration formed of a suitableelectrical insulating material such as linen base phenolic orglass-epoxy, having a plurality of commutator members here shown as ringsegments 12, 12, 13, 13' arranged thereon. In the illustrated embodimentthe commutator rings are of the segmented type, each ring segmentextending through an arc of slightly less than so as to provideseparation between rings Four commutator ring segments are shown, but itwill be appreciated by those skilled in the art that a greater or lessermember may be employed. Arranged on arcs having radii of curvaturelarger than the radii of curvature of the commutator ring segments are aplurality of contacts 14, 14, and 15, 15'. The angles sub-tended by thearcs along which the contacts are arranged are preferably substantiallyequal to the arcs sub-tended by the commutator ring segments with whichthe contacts are to be electrically connected. As shown in FIG. 4,groups of contacts 14, 14' and 15, 15 are associated respectively withcommutator ring segments 12, 12' and 13, 13'.

Hollow bored contact stems, as shown in FIG. 3, extending through thecontact plate 11 provide contact terminals 20 for coupling of thecontacts to an electrical circuit to be controlled by the switch 10.commutator terminal strips 22 are electrically coupled to the commutatorring segments through the contact plate 11. A flanged bearing sleeve 25is centrally arranged, extending through contact plate 11 at the centerof the arcs of the commutators and contacts.

Brush block assembly 30, as shown in FIGS. 3 and 4, comprises a brushsupporting plate 31 of a circular configuration having a diametersubstantially equivalent to the outer diameter of that of the outer arcof contacts 15, 15'. Plate 31 is fabricated of an electricallyinsulating material similar to that of the contact plate 11 and isformed with spaced pairs of openings 32, 33, 34 and 35, extendingthrough plate 31. Four such pairs of openings are here providedcorresponding to the number of commutator ring segments and contactgroups respectively.

U-shaped brush members 37, each having an inner commutator engaging leg38, and an outer contact engaging leg 39 are arranged with legs 38 and39 extending respectively through the inner and outer of the pairs ofopenings 32, 33, 34 and 35 as best seen in FIGS. 3 and 4.

A cantilever or leaf spring 45 of a configuration as shown in FIGS. 1, 3and 4 is riveted or otherwise secured at 46 to brush supporting plate31. Pressure foot 48 having an arcuate free edge extends from the end ofspring 45 into fulcruming contact with brush member 37. The arcuateconfiguration of the free edge of foot 48 provides a fulcrum for brushmember 37 due to the point contact between spring 45 and brush member 37thereby permitting rocking of the brush member with respect to plate 31about the contact point and also concentrating the spring forces at thepoint of contact, and insuring dependable contact at such point.

'pin 57 is secured to plate 55 for a purpose to be made hereafterapparent. Headed detent supporting pivot pin 60 is similarly secured toplate 55 along with spring stop pin 61.

Shaft 65 extends rotatably through bushing 56 and is upset or otherwiseshaped to form flare 57 as shown in FIG. 3. Beyond thefiare 57 the shaftextends through collar 50 which is secured to the shaft 65 by means ofset screws 51. The free end of shaft 65 extends rotatably throughbearing sleeve 25. Knob 67 is secured to the end of shaft 65 adjacentmounting plate 55 by knob set screw 68.

Star wheel 70, as shown in FIGS. 3 and 5, is fixed to shaft 65 forrotation therewith. Spaced stops 71 and 72 are formed in the surface ofstar wheel 70 positioned to contact stop pin 57 on mounting plate 55.The angle between stops 71 and 72 between which pin 57 engage is equalto the angle sub-tended by the commutator segments and the contactgroups. The number of teeth on star wheel 70 is such as to provide anintertooth valley 75 for each desired switch step.

Detent 80 is pivoted on detent pivot pin 60 and is formed with detentroll 81 on its free end. Roll '81 rides over the teeth of star wheel 70into intertoo'th valleys 75. Hairpin spring 83 is wound about detent pin60 with one spring leg bearing against spring stop pin 61 and the otherspring leg bearing against detent spring pin 84 to bias roll 81 againstthe star wheel.

The aforedescribed mounting plate 55, and contact plate 11 aremaintained in desired assembled relationship with respect to the othercomponents by means of machine screws 85 extending through plates 55 and11, and through spacers 86 arranged between the plates. Nuts 87 engagescrews 85 to maintain the switch components in assembled relationship.

In use of the instrument switch above described, the commutatorterminals and contact terminals are electrically connected inconventional fashion to the circuits to be controlled by the switch. Itis preferred that alternate contacts of each group be inactive dummiesproviding land for the brushes to wipe over thereby insuring a breakbefore make mode of operation and insuring a smooth wiping action of thebrushes over the contact surfaces.

After desired circuit connections are made, manual manipulation of knob67 to rotate shaft 65 effects rotation of star wheel 70 and brush blockassembly 30. The detent 80 is cammed away from the center of star wheel70 over the tooth of the star wheel into the star wheels next intertoothvalley 75. Where alternate contacts are dummies, the rotation of shaft65 permitted by the star wheel 70 and detent 80 will provide forstepping of the brush assembly 30 through an are having an angle equalto the angle of the are between active contacts. Thus, at each steppingof the brush block assembly, the brushes will move from one activecontact in any contact group to another.

' In order to insure that the brush members only move to make aconnection between a given commutator ring segment and its associatedcontact group, stops 71 and 72 in engaging limit pin 57 limit themovement of the brush plate assembly 30 through this desired range.

It will be observed that the legs 38 and 39 of brushes 37, as best shownin FIG. 1, are chamfered at their edges thereby increasing the facilitywith which the brushes ride onto the contact surface. Any irregularitiesin the path of travel of the brushes over the commutator rings andcontacts is accommodated by the free floating mount of the brush 37 onbrush supporting plate 31. The brush rocks on fulcrum provided by thepoint of contact be tween the foot 48 of cantilever spring 45, with thespring forces exerted on the spring remaining constant. c

The instrument switch above described provides means for insuringdesired positive metal to metal wiping contact between the brush membersand the contacts and commutation rings, thus reducing electricalresistance and distributing frictional wear to extend the service lifeof' the switch.

As many changes could be made in the above construction, and manyapparently widely different embodiments ,1

of this invention could be made without departing from the scope of theclaims, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. An electrical switch comprising a contact plate, a plurality ofspaced contacts arranged in a ring on said contact plate, an arcuatecommutator member spaced from said contacts, a rotatable brushsupporting plate, a free floating brush member of U-shaped configurationcarried by said support plate and movable over said commutator memberand said contacts, a cantilever spring of relatively thin sheet springstock carried by said support plate and biasing said brush memberagainst said contacts and commutator member to engage the same, and afoot on said cantilever spring having an arcuate edge providing afulcrum on which said brush member may rock, and providing substantialpoint contact between the cantilever spring and the brush.

' 2. An electrical switch comprising a contact plate, a. plurality ofconcentric arcuately arranged groups of contacts on said contact plate,a plurality of commutator ring segments corresponding in number to saidgroups of contacts on said contact plate, a brush supporting platerotatably mounted adjacent said contact plate, said brush supportingplate being formed with a plurality of pairs of spaced openings, one ofthe openings of said pair being aligned with one of said corn-mutatorrings and the other of the openings of one of said pairs being alignedwith one of said contact groups, a plurality of brush memberscorresponding in number to said groups of contacts loosely carried bysaid brush supporting plate, each of said brush members being U-sha'pedin configuration with one of the legs of said brush member extendingthrough one of said openings and another of the legs of said brushmember extending through the other of said openings, thereby bridgingthe gap between said commutator segment and said group of contacts, acantilever spring on said brush supporting plate, and 'a foot on saidcantilever spring having an arcuate free end engaging said brush memberto provide a fulcrum on which said brush member may rock.

References Cited by the Examiner UNITED STATES PATENTS 7 698,200 4/1902Hinds 2001l.23

969,055 8/1910 Hammond 20011 2,090,505 8/1937 Uhle ZOO-11.22 2,186,6381/1940 Hall 20011.24 2,402,736 6/1946 Davis 200ll.22 2,430,215 11/1947Doucette 200164 2,489,626 11/1949 Doucette 200-11.22 2,504,027 4/ 1950Kuh'lman 20011 2,771,520 11/1956 Stevens ZOO-15 ROBERT K. SCHAEFER,Primary Examiner.

BERNARD A. GILHEANY, KATHLEEN H. CLAFFY,

E. JAMES SAX, Examiners.

I. R. SCOTT, Assistant Examiner.

1. AN ELECTRICAL SWITCH COMPRISING A CONTACT PLATE, A PLURALITY OFSPACED CONTACTS ARRANGED IN A RING ON SAID CONTACT PLATE, AN ARCUATECOMMUTATOR MEMBER SPACED FROM SAID CONTACTS, A ROTATABLE BRUSHSUPPORTING PLATE, A FREE FLOATING BRUSH MEMBER OF U-SHAPED CONFIGURATIONCARRIED BY SAID SUPPORTING PLATE AND MOVABLE OVER SAID COMMUTATOR MEMBERAND SAID CONTACTS, A CANTILEVER SPRING OF RELATIVELY THIN SHEET SPRINGSTOCK CARRIED BY SAID SUPPORT PLATE AND BIASING SAID BRUSH MEMBERAGAINST SAID CONTACTS AND COMMUTATOR MEMBER TO ENGAGE THE SAME, AND AFOOT ON SAID CANTILEVER SPRING HAVING AN ARCUATE EDGE PROVIDING AFULCRUM ON WHICH SAID BRUSH MEMBER MAY ROCK, AND PROVIDING SUBSTANTIALPOINT CONTACT BETWEEN THE CANTILEVER SPRING AND THE BRUSH.